Postmortem Changes in ATP, Creatine Phosphate, and Lactate in Sardine Muscle

Postmortem changes were followed in sardines stored in ice. Fast (“white”) muscle creatine phosphate began decreasing from 25 μmol/ g immediately after death. ATP concentration remained about 10 μmol/ g and began decreasing after 2 hr when rigor mortis onset was observed. ATP decreased rapidly when creatine phosphate concentration reached a level similar to ATP, and was 2 μmol/g after 8 hr when full rigor was observed. Lactate accumulation proceeded parallel to ATP degradation (correlation coefficient r = ‐0.995) and the degree of rigor mortis (r = ‐0.989). In contrast, sardine slow muscle was low in creatine phosphate (1 μmol/g) and ATP (5 μmol/g), both of which decreased immediately after death. Lactate accumulation was low in this muscle and correlation with rigor mortis progress was lower (r = ‐0.902) than for fast muscle.